cGMP is biosynthesized from guanosine triphosphate (GTP) by the action of guanylate cyclase and metabolized to 5′-GMP by the action of cGMP-PDE, during which cGMP plays various roles as a secondary transmitter in cellular signal transduction in the body. Particularly the action of cGMP, which is of critical importance in the functional modulation of cardiovascular system, is well known. Therefore, inhibition of the action of cGMP-PDE leads to the prophylaxis or treatment of the diseases caused by the promotion of metabolism of cGMP. Examples of such diseases include angina pectoris, heart failure, cardiac infarction, hypertension, pulmonary hypertension, arteriosclerosis, allergic diseases, asthma, renal diseases, cerebral function disorders, immunodeficiency, ophthalmic diseases, disorders of male or female genital function and the like.
There are a number of reports on a compound having a PDE inhibitory activity (e.g., WO9853819 and references cited therein). However, only a small number of reports deal with a compound having a monocyclic pyrimidine skeleton and showing a PDE inhibitory activity, which are limited to JP-A-2-295978, JP-A-3-145466, JP-A-7-89958, Korean J. of Med. Chem., vol. 8, p. 6 (1998) and the like.
PDE is known to include at least 7 isoenzymes [e.g., Annual Reports in Medicinal Chemistry, vol. 31, p. 61 (1996), Academic Press, San Diego]. Of those isoenzymes, PDE I, II, III, IV and V are widely distributed in the body. It is well known that inhibition of plural isoenzymes results in unpreferable occurrence of side effects.
It is therefore an object of the present invention to provide a potent and selective PDE inhibitor.